1. Field of the Invention
This invention relates to semiconductor wafers with apertures to facilitate handling and to processes for forming and handling such wafers.
2. The Prior Art
Semiconductor wafers cut from large ingots are usually circular or elliptical. A small segment may be removed from one part of the circular edge corresponding to a predetermined crystallographic orientation. These wafers are the basic structures, or substrates, for manufacturing a wide variety of semiconductor devices, including diodes, transistors, integrated circuits, and the like. The manufacture of any of these devices comprises a number of steps, some more than others, and between each step and the next the wafer usually needs to be moved from one place to another, or at least repositioned. The wafers are easily damaged, both physically and by chemical contamination, and the usual means for handling them is a pair of tweezers. In some cases, a single wafer may have to be handled 200 times in the manufacture of a complex integrated circuit device, and with such a large number of repetitions, even the most careful handling may cause surface deterioration of the wafer or cracks in the wafer so as to render at least part of the wafer unusable. Such losses are expensive, for even if the semiconductor material can be salvaged and reprocessed, there is a loss of the time involved in carrying out manufacturing steps on that part of the wafer that later is damaged and cannot be used.
It is one of the objects of the present invention to provide semiconductor wafers that can be easily handled without touching the main surfaces of the wafers.
The novel wafers of this invention are formed by a process that requires boring a semiconductor wafer in such a way as to form a hole of selected cross-sectional shape and axial orientation.
A further object of this invention is to provide an improved process for forming apertured semiconductor wafers and improved means for boring holes in semiconductor ingots.
Heretofore semiconductor wafers have been sliced by disc saws having either internal or external cutting edges. In either case, the cutting edge must move completely through the ingot to make each slice. This requires that the radial distance between the cutting edge and the support means for the blade be at least as great as the diameter of the ingot, and the greater this radial distance, the more flexible the blade of a given thickness. Flexibility is detrimental to accurate cutting.
It is a further object of the present invention to reduce this relative radial movement of the cutting blade and ingot to less than half the diameter of the ingot so that blades having smaller free radial dimensions, and therefore greater rigidity, can be used.